Habit and leaf form. Trees (small), or shrubs; laticiferous, or non-laticiferous and without coloured juice. Leaves cauline. Stem internodes solid. Leaves alternate (often clustered); ‘herbaceous’, or leathery; petiolate; non-sheathing; simple. Leaf blades entire; elliptic, or oblong (oblong-elliptic), or obovate (rarely); pinnately veined; cross-venulate; attenuate at the base. Leaves with stipules. Stipules minute; caducous. Leaf blade margins entire, or serrate, or dentate. Leaves without a persistent basal meristem. Leaf anatomy. Hairs absent (or nearly so). Extra-floral nectaries absent.
Reproductive type, pollination. Fertile flowers hermaphrodite. Unisexual flowers absent. Plants hermaphrodite. Entomophilous.
Inflorescence and flower features. Flowers aggregated in ‘inflorescences’; in cymes (usually), or in racemes, or in panicles. The terminal inflorescence unit cymose, or racemose. Inflorescences terminal, or leaf-opposed; cymes and racemes few-flowered, panicle terminal, short and oblong, cymes pedunculate. Flowers pedicellate; bracteate (minute, subtends the peduncle); bracteolate (K); usually small; regular; 4–5 merous; cyclic; nearly always tetracyclic. Hypogynous disk present; intrastaminal; annular. Perianth with distinct calyx and corolla; (4–)8–10; 2 -whorled; isomerous. Calyx present; 5 (nearly equal); 1 -whorled; gamosepalous (fused at the base only); entire (or erose), or lobed; when not entire, blunt-lobed; imbricate, or valvate; regular. Calyx lobes elliptic, or ovate, or orbicular. Corolla present; 5; 1 -whorled; polypetalous; imbricate; regular; green, or white, or cream (white to pale green, cream to yellowish green). Petals elliptic, or oblong to orbicular (or semicircular). Fertile stamens present, or absent (in functionally female flowers). Androecial members definite in number. Androecium 5. Androecial members free of the perianth; all equal; free of one another; 1 -whorled, or 2 -whorled. Androecium exclusively of fertile stamens, or including staminodes. Staminodes sometimes (2–)3–5 (alternating with the stamens). Stamens 5; all more or less similar in shape; isomerous with the perianth; oppositisepalous (on margin of cupular disc). Anthers dehiscing via longitudinal slits; extrorse, or introrse; unilocular to bilocular; bisporangiate, or tetrasporangiate. Pollen shed in aggregates, or shed as single grains; when in aggregates in tetrads, or in polyads. Fertile gynoecium present, or absent (in functionally male flowers). Gynoecium 2–5 carpelled (usually with all but one abortive). The pistil 1–5 celled. Gynoecium syncarpous; synstylovarious, or eu-syncarpous; superior (adnate to disc so seems inferior), or partly inferior (K). Ovary plurilocular; 2–5 locular (perfectly or imperfectly); sessile. Gynoecium non-stylate (obsolete), or stylate (KCLB). Styles 1 (or 0); attenuate from the ovary; apical. Stigmas 1–5 (3 in West Australian species); where only 1, 2–5 - lobed. Placentation axile. Ovules 2–10 per locule; pendulous, or ascending; apotropous; with ventral raphe, or with dorsal raphe (when pendulous); anatropous.
Fruit and seed features. Fruit fleshy, or non-fleshy; not an aggregate (woody); dehiscent; a capsule, or a berry, or a drupe, or a samara, or achene-like. Capsules loculicidal. Fruit several. Seeds endospermic, or non-endospermic. Endosperm when present, ‘more or less’ oily. Seeds winged, or wingless. Embryo well differentiated. Cotyledons 2 (large, flat, foliaceous). Embryo straight.
Etymology. After Dixon Denham (1786–1828), traveller in Africa, accompanied Clapperton and Oudney's expedition to Lake Chad and Bornu in Nigeria.
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Western Australian Herbarium (1998–). FloraBase—the Western Australian Flora. Department of Biodiversity, Conservation and Attractions. https://florabase.dpaw.wa.gov.au/